The sun has some serious star power and a definite flair for drama, but getting a good look at this celestial beauty has a specific set of rules.
There are many options for viewing the sun safely. The only option you do not have is your own unaided eyes. Looking at the sun directly, even with a quality pair of sunglasses on, is dangerous. Eye tissue is not like other tissue – once it is damaged, it often remains damaged. Looking at the sun through your telescope without any protection is even more dangerous, for you and your telescope.
Your safe options for observing the sun, including big events like the 2012 Venus Transit, come in a wide range – everything from the sophisticated to the everyday. On the everyday side of the spectrum, you have a simple sun funnel, which you can make at home and attach to any refracting telescope, and eclipse glasses, which sell for about a dollar.
At the higher end of the price range, there are dedicated solar telescopes. These represent a significant investment, but they are a lot of fun to use.
A Herschel Wedge is another option to consider, at least for refractor telescopes. These optical prisms filter out the majority of the sun's light that travels down the optical path of your telescope and direct it away from your eye so you can use the remaining light to enjoy a view of the sun.
A great option for those who already own a quality telescope is a solar filter. These can complement the equipment you already have and offer some great insight into the characteristics of the sun. The best solar filters can help you get a better look at our closest star – sunspots at a minimum, but also other sun-specific wonders such as flares, prominences, spicules, plages, coronal mass ejections and more, in some cases.
Sun filters fit over the end of the optical tube, so you have to know the specific size of your telescope before you buy one. The solar filter needs to fit snugly for safety's sake. You don't want it to come loose and expose you to a dangerous view of the sun.
You will run into many different products when you start to look for a solar filter. The basic types of telescope filters for the sun are:
Hydrogen-Alpha – This type of solar filter blocks all light except for the H-alpha wavelength. They offer an orange-reddish view of the sun that can include solar flares, prominences and much more. These filters are definitely on the higher end in terms of price, but if you are very interested in solar viewing, it might be worth it.
White-Light – This type of telescope filter provides a barrier to almost all of the sun's light transmissions by cancelling out ultraviolet rays and blocking unwanted light. The result should be a nice view of sunspots, convection-cell granulation, eclipses and more.
Calcium-K – These filter out all light except for the calcium-K spectral line and should offer a look at some impressive sun sights, including coronal holes and chromospheric emissions.
Mylar and Polymer – These are the most basic and inexpensive options, but they will still allow you to see the sun as you probably haven't before. Mylar and polymer filters have a reputation for making the sun appear in unnatural colors, including blue, which can be a drawback. Many people prefer to see a more natural, white look at the sun.
Buy the best filter you can fit into your budget and prepare to enjoy the solar sights. One of the best things about a quality sun filter is that it extends the usefulness and enjoyment of your telescope. Your telescope does not need to be exclusively nocturnal. A good solar filter can raise your enjoyment of eclipses and other special events, but you can also break it out on any ordinary afternoon to enjoy all of the fascinating sights of the sun.
Whether or not you ultimately invest in a solar filter, always prepare and protect your eyes in some way when you look at the sun. The stellar views will be worth the trouble.
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